TOXICOLOGICAL AND ABSORPTION ENHANCING EFFECTS OF GLYCOFUROL-75 AND SODIUM GLYCOCHOLATE IN MONOLAYERS OF HUMAN INTESTINAL EPITHELIAL (CACO-2) CELLS

The effects of glycofurol 75 (GF) and sodium glycocholate (GC) on the toxicity and permeability of the human intestinal cell line Caco-2 were studied. The intracellular dehydrogenase activity of the cells was used as a measure of the toxicity. Concentrations of GC from approx. 10 mM inhibited the intracellular dehydrogenase activity and above 40 mM the activity was less than 10% of the initial level. The concentrations resulting in 50% inhibition (IC50) were 24.2 mM (1.2%) and 380 mM (6.8%) for GC and GF respectively. GF concentrations of less than 100 mM did not affect the activity. The effects of GF and GC on the absorption of the hydrophilic marker molecule [C-14]mannitol were studied at concentration levels corresponding to no (23.7 mM GF and 5.1 mM GC), about 25% (117 mM GF and 17.2 mM GC) and 50% (380 mM GF and 24.2 mM GC) inhibition in dehydrogenase activity. The apparent permeability coefficient for mannitol in control monolayers was 5.7 x 10(-8) cm/s. 5.1 mM GC did not enhance the permeability, whereas 17.2 and 24.2 mM enhanced it significantly (p < 0.001). GF (380 mM) did not enhance the permeability. The apparent permeability coefficient of insulin in control monolayers was less-than-or-equal-to 9.8 x 10(-8) cm/s, but varied considerably. 24.2 mM GC enhanced the P(app) significantly (p < 0.001), whereas GF (380 mM) did not affect the absorption of insulin. The Caco-2 cells were studied by transmission electron microscopy after exposure to 380 mM GF for 1 h. Cells exposed to a mannitol solution of the same osmolality as 380 mM GF (about 700 mosm) and untreated monolayers of Caco-2 cells served as controls. GF caused morphological alteration of the epithelial cells resulting in a distorted appearance with disordered microvilli, disorganized terminal web and intracellular vacuols. This effect is problaby due to the high osmolality as the cells exposed to mannitol displayed the same distorted appearance. However, no effect could be observed on the integrity of the apical cell membrane and the tight junctions.